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SurFacE oF objEctS

We identify whether a solid can stalk, roll or slide,

by observing its faces or surfaces. That means
stalking, rolling or sliding of objects depends upon

the nature of their surfaces.
Let us try to make a stalk of cubical blocks as well

as balls.

Blocks can be stalked easily but we cannot put a ball on another
ball without external support. This is because a cube has a plane
surface and a ball has a curved surface.

If a solid is made up of only plane faces, it slides.
Here, we can see that the pencil box has plane faces. So, the box

is sliding.

If a solid is made up of only curved faces or surfaces, it rolls.

Here, we can see that the ball has only a curved surface.

So, the ball is rolling.

Some solids are made up
of both plane and curved

faces. Such objects can
roll as well as slide.

Here, we can see that the juice-can has both
plane and curved surfaces. So, it is rolling and sliding.

Practice time 8d

1. Look at the given objects. Find which can roll, slide or stalk.

Object

roll

Slide

Stalk

146 Mathematics-2